Method of obtaining measurement data using a sensor application interface

ABSTRACT

A method involves, via a sensor application interface, 1) receiving, from an application, a measurement request associated with a quality-of-service control; 2) in accord with the quality-of-service control, obtaining measurement data from a sensor; and 3) returning to the application i) the measurement data obtained from the sensor, and ii) an indicator of accuracy of the measurement data.

CLAIM OF PRIORITY UNDER 35 U.S.C. §119

The present Application for Patent claims priority to U.S. patentapplication Ser. No. 11/688,824 entitled “Method Of ObtainingMeasurement Data Using A Sensor Application Interface” filed Mar. 20,2007, which claims priority to Provisional Patent Application No.60/784,608 entitled “Sensor Application Interface” filed Mar. 20, 2006,assigned to: the assignee hereof and hereby expressly -incorporated byreference herein.

BACKGROUND

There are many sensors on the market today. These sensors are designedto convert a physical phenomenon into an electrical signal. For example,

Barometric Pressure Sensor

-   -   Measures atmospheric pressure        -   Altitude        -   Weather

Accelerometer

-   -   Measures direction of gravity        -   Linear movement        -   Tilt (Roll, Pitch)        -   Shock sensing        -   Free-fall

Gyroscope

-   -   Measures Coriolis effect        -   Heading Changes        -   Rotation

Magnetic Field Sensor

-   -   Measures direction of magnetic field        -   Compass        -   Absolute Heading

Accelerometers are the most widely used MEMS sensors with millionsintegrated into cars by the automotive industry. As said above, thelinear accelerometers can sense the linear motion and can provide ameasure of tilt. With a 3D accelerometer, motion in (x, y ,z) can besensed. In .addition, the direction of the gravity can be used toestimate the roll (θ) and pitch (φ) (see FIG. 1).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a single-sensor accelerometerconfiguration;

FIG. 2 is an illustration of a two-sensor accelerometer configuration;

FIG. 3 is an illustration of linear movement of the two sensors shown inFIG. 2; and

FIG. 4 is an illustration of angular movement of the two sensors shownin FIG. 2.

DETAILED DESCRIPTION

Unfortunately, in wide number of cases it is difficult to differentiatebetween a linear motion (acceleration in x, y, z) and the change in theorientation of the device and the corresponding change in roll andpitch. Furthermore, a change in the heading (aka yaw or azimuth, ψ) cannot be sensed by the linear accelerometers at all. For sensing thechange in the heading, gyroscopes are commonly used. However, gyroscopesare expensive, large and complex structures and therefore more expensivethan accelerometers.

What is needed is a solution which can reliably deliver a measure oflinear motion and orientation. This invention discloses a method ofintegrating two 3D linear accelerometers in order to measure and provide6D information (x, y, z, θ, Φ, ψ), see FIG. 2. Since, accelerometersdeliver second momentum the measurements need to be integrated once toget the rate of change and second time to get the absolute measures.

Two 3D accelerometers deployed at opposite corners of the board cansense the linear movement—sensors produce similar outputs (see FIG. 3),and sense orientation changes—sensors produce opposing outputs (see FIG.4).

One key requirement is near simultaneous read-out of the measurementsfrom both accelerometers.

In order to be able to efficiently use sensors in various applications,a sensor must provide several functions: control capability, measurementoutput and quality control.

An application programming interface (API) is defined which in additionto the control and common measurement output interface adds a qualitycontrol. The quality control has a bi-directional purpose. For example,on the input quality-of-service (QoS) control allows the sensor user(application developer) to prioritize the time per measurement vs.accuracy of the sensor measurement, it can specify how often themeasurement is performed (periodic) and the duration of measurementperiod, define the event triggering the sensor measurement, thresholdlevel for sensor output to trigger the measurement processing, length ofmeasurement filtering (time constant), etc. The sensor QoS will add theaccuracy measures to the raw measurement values: directional informationaccuracy, tilt accuracy, acceleration accuracy, rate of rotationaccuracy, pressure accuracy, temperature accuracy, etc. It can also addspecific event outputs such as “shock detected”, (e.g., accelerationmagnitude above 1000 g was detected), etc.

The availability of sensor QoS control functionality facilitates sensorintegration and allows successful integration of the measurements from,multiple sensors for various applications utilizing sensor measurements.

TABLE 1 Example Sensor Measurement Specification Measurement Data typeUnit (resolution) Data range Geomagnetic Compass Direction angle 16-bitsigned integer 0.1° 0 to 3599 (0° to 359.9°) Direction angle accuracy4-bit unsigned 0 to 15° integer Magnetic vector, 16-bit signed integer0.1 μT −15000 to 15000 magnitude (−1500 μT to 1500 μT) Magnetic vector,x 16-bit signed integer 0.1 μT −15000 to 15000 (−1500 μT to 1500 μT)Magnetic vector, y 16-bit signed integer 0.1 μT −15000 to 15000 (−1500μT to 1500 μT) Magnetic vector, z 16-bit signed integer 0.1 μT −15000 to15000 (−1500 μT to 1500 μT) Orientation angle Pitch 16-bit signedinteger 0.1° −900 to 900 (−90.0° to 90.0°) Roll 16-bit signed integer0.1° −1800 to 1800 (−180.0° to 180.0°) Orientation angle 4-bit unsigned0 to 15° accuracy integer Linear Acceleration Acceleration vector,16-bit signed integer 0.1 mg −30000 to 30000 magnitude (−3000 mg to 3000mg) Acceleration accuracy 4-bit unsigned 0 to 10 mg integer Accelerationvector, x 16-bit signed integer 0.1 mg −30000 to 30000 (−3000 mg to 3000mg) Acceleration vector, y 16-bit signed integer 0.1 mg −30000 to 30000(−3 g to +3 g) Acceleration vector, z 16-bit signed integer 0.1 mg−30000 to 30000 (−3 g to +3 g)

The previous description of the disclosed embodiments is provided toenable any person skilled in the art to make or use the presentinvention. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments without departing from thespirit or scope of the invention. Thus, the present invention is notintended to be limited to the embodiments shown herein but is to beaccorded the widest scope consistent with the principles and novelfeatures disclosed herein.

1. (canceled)
 2. A method, comprising: via a sensor applicationinterface, receiving, from an application, a measurement request fordirection and orientation associated with a quality-of-service control;in accord with the quality-of-service control, obtaining measurementdata from a plurality of similar sensors corresponding to the directionand orientation; and returning to the application i) the measurementdata obtained from the plurality of sensors, and ii) an indicator ofaccuracy of the measurement data.
 3. The: method of claim 2, wherein theplurality of sensors comprise at least two accelerometers and whereinthe step of obtaining measurement data includes integrating measurementsfrom each of the at least two accelerometers.
 4. The method of claim 3,wherein integrating measurements, from each of the at least twoaccelerometers provides 6 degrees of information.
 5. The method of claim4, wherein the 6 degrees of information include linear information (x,y, z) and orientation information (θ, φ, ψ.
 6. The method of claim 2,wherein the indicator of accuracy of measurement data is selected from agroup of indicators consisting of: directional information accuracy,tilt accuracy, acceleration accuracy, rate of rotation accuracy,pressure accuracy, or temperature accuracy.
 7. The method of claim 2,wherein the step of returning to the application includes returningevents.
 8. The method of claim 7, wherein returning events includesreturning a shock event.
 9. The method of claim 5, wherein at least oneof the linear information and orientation information is selected fromthe group of linear information consisting of: direction angle, magneticvector magnitude, magnetic vector x, magnetic vector y, magnetic vectorz, pitch, roll, acceleration, acceleration vector x, acceleration vectory, or acceleration vector z.
 10. An apparatus having a sensor to senselinear and orientation information, the apparatus comprising: a firstaccelerometer; and a second accelerometer, wherein the first and secondaccelerometers are integrated to sense linear information by producingsimilar output and orientation information by producing opposingoutputs, and wherein the linear and orientation information is beingprovided to an application along with a quality-of-service control. 11.The apparatus of claim 10, wherein the first accelerometer and thesecond accelerometer are oriented in a plane.
 12. The apparatus of claim11, wherein the first and second accelerometers measure six degrees ofinformation.
 13. The apparatus of claim 12, wherein the 6 degrees ofinformation include linear information (x, y, z) and orientationinformation (θ, φ, ψ.
 14. The apparatus of claim 10, wherein the firstaccelerometer and the second accelerometer register event information.15. The apparatus of claim 14, wherein event information comprises anabrupt change in at least one of linear or orientation information. 16.The apparatus of claim 15, wherein the abrupt change is designated as ashock.
 17. The apparatus of claim 13, wherein at least one of the linearinformation and orientation information is selected from the group oflinear information consisting of: direction angle, magnetic vectormagnitude, magnetic vector x, magnetic vector y, magnetic vector z,pitch, roll, acceleration, acceleration vector x, acceleration vector y,or acceleration vector z.
 18. An apparatus comprising: first means formeasuring linear direction information; second means for measuringlinear direction information, wherein the first means and the secondmeans are integrated to sense linear information by producing similaroutput and orientation information by producing opposing outputs, andwherein the linear and orientation information is being provided to anapplication along with a quality-of-service control.
 19. The apparatusof claim 18 wherein the first means is a first accelerometer.
 20. Theapparatus of claim 19, wherein the second means is a secondaccelerometer oriented in a plane with the first accelerometer.